This invention relates generally as indicated to redundant drive mechanisms for a direct drive valve and force motor assembly, whereby should a failure occur in one of the drive mechanisms, the valve can still be operated through another drive mechanism and vice versa.
In certain types of high pressure fluid proportional servo control systems such as a control actuation system for aircraft in which the fluid pressure may for example be on the order of 1000 psi or more, it has been found advantageous to use a direct drive valve of relatively short stroke. For such applications, it would be desirable to provide a redundant drive mechanism between the valve member and force motor used to drive the valve, whereby should one of the drive mechanisms fail, the force motor can still be used to drive the valve through another drive mechanism and vice versa. Also, it would be desirable to provide for degraded valve performance in the event of a breakage of the valve plunger.